Proceedings of the XLVI Italian Society of Agricultural Genetics - SIGA Annual Congress

Giardini Naxos, Italy - 18/21 September, 2002

ISBN 88-900622-3-1

Poster Abstract - 3.28

ORGANIZATION AND EVOLUTION OF GST MULTIGENE FAMILY IN ARABIDOPSIS THALIANA

SANTELIA D., SORANZO N., MIZZI L., PÈ M.E.

Dip. di Genetica e di Biologia dei Microrganismi, Milano

GSTs, Arabidopsis, chromosomal location, gene duplication

The Arabidopsis Genome Initiative (AGI) has released the complete sequence of Arabidopsis genome. A surprising observation is that despite consisting of only 140 Mb, much of the Arabidopsis genome is internally duplicated and contains many small gene families.

Duplication of ancestral genes, followed by the divergence of both copies, is one of the mechanisms leading to the production of new functional proteins which enable organisms to evolve into a higher form. The understanding of the biological function of a gene requires the analysis of the structure, expression and organization of the entire gene family. Indeed, in order to be able to associate orthologues between different model organisms, and hence to assign biological function to these genes, the classification of every paralogue from each genome is an essential step. A systematic analysis of multigene families provides also important clues for the understanding whole genome evolution and plasticity.

In the present study we characterized the structure and the organization of all the paralogues of Arabidopsis glutathione S-transferase (Gst) gene family in order to throw light on its evolution. GSTs have a crucial role in the detoxification of several toxic compounds, including herbicides and heavy metals.

In silico analyses, namely gene structure predictions and sequence comparisons were used.

Sequence databases screening led to the identification of 48 genes belonging to Gst family. All members have been classified into four subfamilies based on sequence similarity and gene structure. Gst genes have been localized on the genome using the AtDB physical map of the genome of Arabidopsis. Various copies of the Gst genes are dispersed within the genome or are duplicated in tandem, up to seven adjacent genes, suggesting that the evolution of this family occurred through a series of subsequent duplications, probably followed by reciprocal translocation of chromosomes fragments. High sequence conservation in coding as well in non-coding regions of the genes clearly demonstrates recent duplications events. Phylogenetic approach was also employed, aiming to elaborating an evolutionary model for the dynamics of the Gst gene family evolution. Conclusions were based on relationships established between evolutionary trees, chromosome location and sequence similarity analysis of the paralogues.